Method and apparatus for making a high resolution light pattern generator on a transparent substrate

ABSTRACT

A light pattern generator that can be used to form a gobo for use in a projection optical system. A transparent plate is coated with a stack that is absorptive and reflective. The stack is formed to be ablatable in the form of a pattern. The stack can have multiple different layers with multiple different characteristics, all of which are ablated by the laser.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Ser. No.12/495,484 filed Jun. 30, 2009, now U.S. Pat. No. 8,310,751 issued Nov.13, 2012, which claims priority from provisional application Ser. No.61/076,822, filed Jun. 30, 2008, the entire contents of which areherewith incorporated by reference in its entirety.

BACKGROUND

A significant feature of stage lighting systems is the projection ofimages by stage lighting instruments. Images are typically formed bypassing a light beam through a light pattern generator or “gobo” andprojecting the image formed thereby. A gobo therefore operates as alight stencil, blocking certain portions of the light beam and passingother portions. A typical configuration for projecting a pattern oflight has a gobo placed in a projection gate located at a focal plane ofa projection lens and illuminated by a light source. A typicaltheatrical lighting projector, also called a luminaire comprises a lightsource, a reflector which focuses light rays to the focal plane, and oneor more lenses to project an image of the gobo at the focal plane.

It is desirable to make the projector, and thus the gobos, as small aspossible. For this reason, it is often necessary to focus the source'senergy into a very small area. This creates intense heat at the focalplane. Typically, heat resistant gobos have been fabricated as a layerof light reflective materials, such as aluminum deposited on a surfaceof a transparent plate such as heat resistant glass. The lightreflective layer has an opening which is in the shape of the image. Aportion of the light beam passes through the opening to produce a beamhaving the shape of the image. The reflective layer serves to reflect aportion of the light beam which does not pass through the opening.

Glass gobos of this type are very resistant to the intense heat presentat the projection lens focal plane. Glass gobos of this type aremanufactured by a relatively expensive and time-consuming process, e.g.,that described in U.S. Pat. No. 4,779,176.

The process described in U.S. Pat. No. 4,779,176 requires a layer ofpositive photoresist material to be deposited in the shape of a desiredimage onto a large, thin sheet of transparent glass. A thin layer ofaluminum is then deposited over the glass and the photo resist layer. Amulti-layer dielectric coating deposited over the aluminum layer forms a“dark mirror”, which is a low reflectivity surface that absorbs visiblelight. The glass sheet and the various coatings are then exposed tosolvents which dissolves the photo resist and lifts all the layers ofmaterial immediately over the photo resist while having no effect on theglass. The solvents etch process produces an opening through thedeposited layers which is in the shape of the desired image.

This process requires fabricating a photo mask having the desired imageformed therein to facilitate deposition of the photo resist layer. Dueto the significant lead times required to manufacture the photo mask,and thus the finished gobos, this process is not typically suitable forsmall, “made-to-order” production runs.

In an effort to overcome the expense and time required to quicklyproduce glass gobos, prior art methods have employed a laser operatingin the near IR to ablate reflective material from a transparentsubstrate. Such methods are described in U.S. Pat. No. 5,728,994.

As described in U.S. Pat. No. 5,728,994, a light reflective layer isdeposited on a surface of a transparent plate. A laser marking systemwrites an image onto the transparent plate having a reflective layerbonded thereto. The reflective layer is highly reflective to visiblelight and is absorptive of certain wavelengths of near infra-redradiation, in the range of 850 to 2000 nm. The reflective layer of theblank gobo absorbs the energy of the laser beam and is ablated away fromthe transparent plate, leaving an opening in the shape of the desiredimage. The reflective layer can be a four-layer stack of enhancedaluminum, applied by a vacuum-deposition process to produce a coatingthat is highly reflective of visible light, absorptive of near infra-redradiation at 1.06 micrometers, and stable at high temperatures.

This prior art operated by depositing on a transparent plate a layer ofreflective material which reflects visible light and absorbs certainwavelengths of near infra-red radiation; generating a laser beam havinga given beam diameter at a certain infra-red wavelength. It may alsodirect the laser beam onto the transparent plate; steering the laserbeam across a surface of the transparent plate; allowing the energy ofthe beam to ablate reflective material from certain areas of thereflective layer; and switching the laser beam on and off to controlwhich areas of the reflective layer are affected by the laser beam.

Drawbacks of the IR Method Include:

1. Back reflections

2. Low resolution

3. Requires the use of a high maintenance laser, water cooled, etc.

1.06 micron lasers are large, and require water cooling. Therefore theyare expensive to maintain, and the minimum spot size is governed by thewavelength of the laser. Typically, this can be, for example, 0.001″when written over a 1.0″ diameter field of view. The resulting imageryis coarse.

SUMMARY OF THE INVENTION

The minimum diameter of a spot of focused laser energy is directlydependent on the laser wavelength. The inventors recognize that use of aUV laser allows for smaller spot sizes than IR lasers and thereforeproduce ablated gobo images with higher resolution.

Embodiments describe projection optical systems, particularly used theprojection of images by stage lighting equipment and to a method andapparatus for making a high resolution light pattern generator on atransparent substrate for use in such equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 shows an embodiment of a substrate for gobos;

FIG. 2 shows an alternate configuration which ablates from the same sideas the light beam is incident;

FIG. 3 shows a system of forming the gobo; and

FIG. 4 shows an alternative configuration.

DETAILED DESCRIPTION

An embodiment describes a light pattern generator for projecting animage with a light beam, where the object to be imaged is a gobo whichshapes the light beam.

The generator 100 includes a transparent substrate 105 for placement inthe light beam with selective coatings on certain areas to form theimage. The transparent substrate 105 may be a borosilicate glass ofapproximately 1.1 mm thickness, having a transmission of about 95% at355 mm. This substrate 105 is coated on the front side with a highefficiency anti-reflective (“HEAR”) coating that is highly transmissivein the 355 nm to 700 nm range. The transparent substrate 105 is coatedon the rear side with a “release layer” 115 that is highly lightabsorptive (e.g., greater than 90%) at 355 nm. On top of that is a darkmirror coating 120 that is highly absorptive in the 400 nm to 700 nmregion of the spectrum is coated on the release layer 115. This iscovered by a dielectric reflector 125.

A laser 140 produces laser light 145 at 355 nm which is focused on thefront side 101 of the coated substrate 100. The laser light is conveyedthrough the substrate, due to the high transmittance of the HEAR coating110. The laser radiation then contacts the release layer 115, which isvaporized in the location of the laser application. This thus ablatesthe release layer, the dark mirror coating, and the highly reflectivecoating. By pulsing the laser and moving the beam, an image is writtenonto the generator 100, thereby forming a gobo from the substrate.

An alternative embodiment may be similar to that in the above, with theHEAR and UV absorber layers removed.

FIG. 4 shows an embodiment where there is a “simplified” configuration.A substrate of borosilicate glass 400 is formed with a top surface 402that faces to the incident light beam, and a bottom uncoated surface404. The borosilicate substrate has a transmission at 355 nm of greaterthan 95%. The top surface 402 is covered with a UV absorbing darkcoating 420 that absorbs most of the incoming light, e.g, reflects lessthan 5% of incoming light (355-700 nm). The coating 420 is covered witha multi layer reflector layer 430 which is formed of multiple layers ofreflector elements. The multi layer reflector may reflect more than 93%of 400-700 nm radiation.

Yet another embodiment 200, shown in FIG. 2, includes a transparentsubstrate 205 for placement in the light beam. The transparent substrate205 is uncoated on the front side 206 (which is the side that receivesthe incident light beam). The transparent substrate is coated on therear side with a “release layer” 210 that is highly absorptive at 355nm. On top of the release layer 210 is a reflective coating 215 that ishighly reflective in the region of 400 nm to 700 nm. On top of that is adark mirror coating 220 that is highly absorptive in the 355 nm to 700nm region of the spectrum.

A UV laser 230 creates laser light 235 at 355 nm which is focused on thefront side 206 of the coated substrate. The laser light is conveyedthrough the substrate and contacts the release layer 210. The laservaporizes and ablates the release layer, the highly reflective coating,and the dark mirror coating. By pulsing the laser and moving the beam,an image is written onto the device, thus forming a gobo.

Another aspect of shown in FIG. 3 comprises an apparatus for making alight pattern generator. The apparatus includes a general purposecomputer 300, a laser marking system 310 at operating in the UV regionat 355 nm, and a galvo system 320 for steering the focused laser beamacross the substrate 330. The general purpose computer 300 serves as ahost computer interface to the laser marking system and galvo systems.The laser marking system writes an image onto a transparent plate havinga reflective layer bonded thereto, the image being dependent upondigital computer data selected at the host computer interface and loadedinto a control unit of the laser marking system. The laser beam has avery narrow beam diameter and a characteristic wavelength in the near UVregion.

The absorbing layer of the blank gobo is absorptive to the energy of thelaser beam and is ablated away from the transparent plate, along withthe reflective coating, leaving an opening in the shape of the desiredimage.

Another aspect comprises a method for making a light pattern generator.The method includes the steps of: depositing on a transparent plate alayer of reflective material which reflects visible light, absorbingmaterial that absorbs visible light, a release layer that absorbscertain wavelengths of near UV radiation, and a HEAR layer, and;generating a laser beam having a very small beam diameter at a certainUV wavelength; directing the laser beam onto the transparent plate;steering the laser beam across a surface of the transparent plate;allowing the energy of the beam to ablate absorbing material fromcertain areas of the reflective layer, which in turn blows off thereflective material; and switching the laser beam on and off to controlwhich areas of the reflective layer are affected by the laser beam.

Although only a few embodiments have been disclosed in detail above,other embodiments are possible and the inventors intend these to beencompassed within this specification. The specification describesspecific examples to accomplish a more general goal that may beaccomplished in another way. This disclosure is intended to beexemplary, and the claims are intended to cover any modification oralternative which might be predictable to a person having ordinary skillin the art. For example, other forms of lighting devices can be used andother materials can be used.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Forexample, this can be used for the blocks that control the laser to makethe pattern on the substrate. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the exemplary embodiments of the invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein, may be implementedor performed with a general purpose processor, a Digital SignalProcessor (DSP), an Application Specific Integrated Circuit (ASIC), aField Programmable Gate Array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. These devices may also be used to select values fordevices as described herein.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

Also, the inventors intend that only those claims which use the words“means for” are intended to be interpreted under 35 USC 112, sixthparagraph. Moreover, no limitations from the specification are intendedto be read into any claims, unless those limitations are expresslyincluded in the claims. The computers described herein may be any kindof computer, either general purpose, or some specific purpose computersuch as a workstation. The programs may be written in C, or Java, Brewor any other programming language. The programs may be resident on astorage medium, e.g., magnetic or optical, e.g. the computer hard drive,a removable disk or media such as a memory stick or SD media, or otherremovable medium. The programs may also be run over a network, forexample, with a server or other machine sending signals to the localmachine, which allows the local machine to carry out the operationsdescribed herein.

Where a specific numerical value is mentioned herein, it should beconsidered that the value may be increased or decreased by 20%, whilestill staying within the teachings of the present application, unlesssome different range is specifically mentioned. Where a specifiedlogical sense is used, the opposite logical sense is also intended to beencompassed.

The previous description of the disclosed exemplary embodiments isprovided to enable any person skilled in the art to make or use thepresent invention. Various modifications to these exemplary embodimentswill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other embodiments withoutdeparting from the spirit or scope of the invention. Thus, the presentinvention is not intended to be limited to the embodiments shown hereinbut is to be accorded the widest scope consistent with the principlesand novel features disclosed herein.

What is claimed is:
 1. A light pattern generator substrate comprising: atransparent plate with front and rear sides; a coating stack bonded toone of said sides of the transparent plate, said coating stackcomprising: a dark coating which absorbs ultraviolet; and a reflectorlayer, coupled to said dark coating.
 2. A substrate as in claim 1,wherein portions of the coating stack bonded to the rear side of thetransparent plate have been removed in the shape of a pattern.
 3. Asubstrate as in claim 2, further comprising a light beam generator,producing a light beam through said pattern.
 4. A substrate as in claim1, wherein said reflector layer has multiple layers of reflectormaterial.
 5. A substrate as in claim 1, wherein said dark coatingincludes a first layer absorptive to radiation at a first range, and asecond layer absorptive to radiation in a second range.
 6. A substrateas in claim 1 wherein said coating stack is formed of first and secondlayers are formed of materials that are ablated by a UV laser.
 7. Asubstrate as in claim 1, further comprising an anti-reflection coatingbonded to the front side of the transparent plate, said coating beingsubstantially transmissive to radiation.
 8. A substrate as in claim 7,wherein said coating stack is on said rear side of said transparentplate.
 9. A substrate as in claim 1, wherein said coating stack is onsaid front side of said transparent plate.
 10. A substrate as in claim7, wherein said anti reflection coating is at least 95% transmissive toradiation in a 350 nm to 700 nm region.
 11. A light pattern generatorfor use in a projection optical system, comprising: a transparent platewith front and rear sides; an anti-reflection coating bonded to thefront side of the transparent plate, said coating being substantiallytransmissive to radiation; a coating stack bonded to the rear side ofthe transparent plate, said coating stack comprising: a first layerabsorptive to radiation at a first range; a second layer absorptive toradiation in a second range; and a third layer reflective to radiationin a third range; said first, second and third layers are formed ofmaterials that are ablated by a UV laser, and wherein portions of thecoating stack bonded to the rear side of the transparent plate have beenremoved.
 12. A system as in claim 11, wherein said anti reflectioncoating is at least 95% transmissive to radiation in a 350 nm to 700 nmregion.
 13. A system as in claim 11, wherein said first range is within10% of 355 nm.
 14. A system as in claim 11, wherein said second layer isat least 90% absorptive.
 15. A system as in claim 11, wherein saidsecond range is from 400 nm to 700 nm.
 16. A system as in claim 15,wherein said third range is from 400 nm to 700 nm.
 17. A system as inclaim 11, wherein said third layer is at least 90% reflective.
 18. Alight pattern generator for use in a projection optical system,comprising: a transparent plate with front and rear sides; a coatingstack bonded to the rear side of the transparent plate, comprising; afirst layer absorptive to first radiation; a second layer substantiallyreflective to a second range of radiation; and a third layersubstantially absorptive to radiation in a third range of the spectrum;wherein portions of the coating stack bonded to the rear side of thetransparent plate have been removed and patterned.
 19. A system as inclaim 18, wherein said first radiation is within 10% of 355 nm.
 20. Asystem as in claim 18, wherein said second layer is at least 90%absorptive.
 21. A system as in claim 18, wherein said second range isfrom 400 nm to 700 nm.
 22. A system as in claim 21, wherein said thirdrange is from 400 nm to 700 nm.
 23. A system as in claim 18, whereinsaid third layer is at least 90% reflective.